In the oil and gas industry, a drill string is used by a drilling rig to drill a wellbore. The drillstring is typically composed of drillpipe and a bottomhole assembly; the latter including the drill bit, drill collars and other drilling related tools. An automated apparatus generally known as an “Iron Roughneck,” may be utilized to make-up and break-out threaded joints of drill pipe in a drill string. Iron Roughnecks have been used in the drilling industry for several years and are commercially available from a number of suppliers. For example, several Iron Roughnecks are manufactured and marketed by National Oilwell, L.P. in Houston, Tex.
An Iron Roughneck generally comprises a two-piece wrench unit and a spinner unit. The spinner rotates a joint of drill pipe relative to a second joint to either screw the pin end of the tool joint of the first joint of drill pipe into the box end of the tool joint of the second joint, or to unscrew the tool joints of the two joints of drill pipe. The wrench unit provides the torque necessary to make-up or break-out the connection. The bottom wrench, which serves as a back-up wrench, grasps the tool joint of the drill pipe suspended in the rotary table or mousehole. The upper wrench grasps the tool joint of the pipe suspended from the derrick and applies either the final make-up, or the initial break-out torque to the connection.
At various times during drilling operations, the Iron Roughneck needs to be moved between several locations on the rig, including the well centerline, one or more mouse holes, and a parking or storage position. Movement of the Iron Roughneck can be difficult due to the size and weight of the unit. Existing Iron Roughnecks may be mounted on a trolley that rides on a pair of parallel tracks. The problem with this configuration is that if multiple locations are desired, such as a mouse hole and the centerline stabbing position, extra tracks are necessary. The more tracks on the deck, the more tripping hazards that are created for the rig personnel. If access to a second mouse hole is desired, then there could be three sets of tracks all converging on a single point.
A second type of Iron Roughneck-positioning device is a telescopic arm, or scissor arm. This type of arm uses hydraulics to telescope the roughneck to the desired location. These telescopic arms are costly and heavy, and they take up substantial space when retracted to the stored or parked position.
A third type of Iron Roughneck-positioning device is a suspended parallelogram apparatus where the Iron Roughneck is suspended from the derrick and a parallelogram device swings the Iron Roughneck into position. Another variation has the Iron Roughneck hanging from an arm mounted on a C-shaped positioning device. The problems associated with these devices are that the distance from the arm base to the pipe is very short, the Iron Roughneck continues to swing after being placed into position (gravity is used to keep it vertical), the Iron Roughneck is difficult to install, the Iron Roughneck is heavy, and the Iron Roughneck is not very adjustable to future positions.
Many of these prior art devices use hydraulic cylinders for lifting and supporting the Iron Roughnecks and thus are susceptible to failure of the cylinders or a power failure. Thus, it would be desirable to have a system that is lightweight, compact in size, easily installed, for the movement of Iron Roughnecks. Such a system could also be used with other drilling tools or equipment which are heavy and/or awkward to move about the drilling rig.